Among the organic polyisocyanates of commercial and economic significance as starting materials for polyurethanes, both rigid and flexible foams, in particular flexible foams, mixtures of diphenylmethane diisocyanate (MDI), polyphenylene polymethylene polyisocyanates, prepolymers based on such materials, and toluene diisocyanate (TDI) are known to be suitable for preparing flexible foams. See, for example, U.S. Pat. Nos. 4,239,856, 4,256,849, 4,261,852 and 4,365,025, 5,070,114, 4,478,960, 4,945,117, 5,369,138, 4,876,292, 5,521,225.
Allophanate modified isocyanates are also known in the art. Various isocyanates containing allophanate groups and processes for their production are disclosed in, for example, U.S. Pat. Nos. 4,738,991, 4,866,103, 5,319,053 and 5,319,054, and European Patents 0,031,650 and 0,393,903.
An improved isocyanate was required to have improved physical properties over TDI, so it needed to be liquid (an advantage over MDI) and have a vapor pressure higher than TDI (hence it's higher molecular weight structure). Surprisingly, such a foam also exhibited improvement in foam properties.
Foams of varying hardness, reasonable physical properties and good humid aged compression sets can be formulated with the present tetralin isocyanates. Physical properties such as elongation and tear were improved.